Katie McGinty joined the Democratic Party's primary race in Pennsylvania for U.S. Senate with the support of influential recruiters, and her fortunes in the wide-open race may ultimately be about more than her ability or her future as a candidate.

It could be a test of whether the Democratic Party's top-level donors, fundraisers, elected officials and like-minded groups can propel a candidate into the good graces of the rank-and-file.

The lineup of McGinty's supporters is relatively breathtaking - including Senate Minority Leader Harry Reid of Nevada, Gov. Tom Wolf, former Gov. Ed Rendell and the state's major labor unions - and certainly rare to see on one side in such a wide-open, high-stakes election for the Democratic Party.

McGinty's chief rival in the four-way race for the Democratic nomination is Joe Sestak, whose icy relationship with some party leaders is shaping this race - just as it shaped the 2010 race he lost by 2 percentage points to Republican Pat Toomey.

"I've never seen that lineup against one candidate in a primary not based on issue positions," said David Landau, chairman of the Delaware County Democratic Party. "I've certainly never seen anything like this based on personality and not issues."

The primary election is April 26. The fall campaign in Pennsylvania promises to be expensive and closely watched, and Republicans say Democrats cannot retake control of the U.S. Senate without beating Toomey, a potentially formidable candidate who is seeking a second term in November.

Sestak's loss to Toomey is viewed through various lenses: He deserves another chance after barely losing to Toomey during a historic year for Republicans. His feuding with party elders during the 2010 campaign - including defeating the late Arlen Specter in the Democratic primary - was a strong enough signal that he is not a team player.

As early as 2013, Sestak, 64, a former Navy vice admiral and two-term congressman, said he was seriously considering running again and Landau and other Sestak supporters around Pennsylvania note that he has spent the intervening years as a regular on the local party event circuit around Pennsylvania, attending hundreds of fundraisers, county dinners and other gatherings.

But doubts about Sestak propelled a search for an alternative by party leaders in Washington. After a few prospective candidates said "no," McGinty, 52, said "yes" and got into the race in August, 15 months after the long-time state and federal government official finished fourth in the 2014 gubernatorial primary.

The problem for the party's heavy hitters is that their one-sided involvement hasn't necessarily gone well for them in top-tier races in recent Pennsylvania history.

Sestak beat Specter, largely thanks to Democratic primary voters who had opposed the Republican-turned-Democrat for decades and weren't about to change.

Kathleen Kane beat Patrick Murphy in the 2012 primary for attorney general, helped by more than $2 million in family money and a campaign visit by Bill Clinton. And Rendell beat Bob Casey in the 2002 gubernatorial primary, although the former Philadelphia mayor was a political celebrity in southeastern Pennsylvania and went on to become the most prolific candidate fundraiser in state history.

The list of McGinty supporters is a virtual who's who of power players in Pennsylvania Democratic Party politics, plus an assortment of U.S. senators and the Washington, D.C.-based Emily's List.

In theory, endorsements can plug candidates into fundraising networks and networks of volunteers who will hand out leaflets, knock on doors and staff phone banks. But in interviews, Rendell and other McGinty supporters tended to downplay the significance of McGinty's super-structure of support, or what a McGinty loss would say about its influence.

"We're in a different time and I would say in the past that (high-powered endorsements) would be a guarantee (of victory)," said Nancy Mills, a McGinty supporter who is the Allegheny County Democratic Party chairwoman. "I think that now people are so well informed and they do their own research and don't necessarily depend on an endorsement."

Sestak, meanwhile, embraces his differences with party leaders, while acknowledging the downside of going against party leaders who can discourage help from major campaign donors. For her part, McGinty has doubled Sestak's fundraising since she entered the race, but she remains behind in available cash and polling.

Rendell, McGinty's campaign chairman, acknowledged that endorsements are not fate - "If they were determinative, then Donald Trump wouldn't exist," Rendell said - and said it still remains to be seen whether McGinty and her backers can raise the millions necessary to air weeks of TV ads.

"If the answer is 'yes,'" Rendell said, "then she's in business."

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Marc Levy covers politics and government for The Associated Press in Pennsylvania. He can be reached at mlevyap.org